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Why Do My Dashboard Lights Dim When I Turn on My Headlights?

Recently, my wife told me she was having trouble seeing the dash lights in her vehicle while driving to work in the mornings. While the fix was very easy, I realized that a lot of people who are not necessarily mechanically savvy might have trouble figuring out the issue. So, I decided to write this article to help people out.

When dashboard lights go dim when the headlights are turned on, it’s usually because modern vehicles automatically adjust the dashboard brightness because of the current time of the day. Try adjusting your vehicle’s dimmer switch to restore the light levels to your desired brightness.

Here are a couple of examples of what a dimmer switch might look like on your vehicle:

Where Is the Dimmer Switch?

Often it’s some kind of dial near where the headlights are turned on. But sometimes it seems as if they’ve hidden it from us.

The dimmer switch is usually found on the left-hand side of the dash in the form of a dial but it is sometimes is the same knob that controls the mileage on the instrument cluster (where the lights are). It could also be on the long switch that sticks out of the side of the steering column.

In rare cases, dimming dash lights can be a warning that your vehicle needs maintenance or repair. The rest of this article will help you pinpoint what is causing the dimming so that you can take steps to resolve it.

How to Know if Dimming Is a Problem

If you find it difficult to see your dashboard alerts and information due to overly dimmed lights, this can be a huge problem. It’s difficult to safely drive when it’s hard to tell how fast you are going. I’ve had this issue before, and it’s rather disconcerting, to say the least.


A common reason for dimmed dashboard lights might be that the dimmer automatically reduces the light level in some vehicles when the headlights are turned on. The idea behind it is that our vision adjusts to nighttime settings and sees the light better under certain conditions, so your car adjusts for it. But before we go down that road, let’s just try an easy adjustment.

Locate the Dimmer Switch

Low dashboard light levels are most often caused by someone accidentally bumping or turning the dimmer switch. Usually, there is a dial on the left side of the dash or on the headlight control switch that sticks out of the side of the steering column. Try turning it up and down to see if that fixes it.

If you don’t can’t find the switch, please consult your vehicle user’s manual. Here is where it is on my Corolla and my wife’s Sienna:

Corolla Dimmer Switch
Sienna Dimmer Switch (They hid it from us!)

Other Potential Causes

If turning up the dimmer switch doesn’t solve the issue, it could be a blown, ineffective fuse, or (less likely) a faulty bulb light. The lights in the dash are designed to last the lifetime of the car, so this is something to have checked as the last resort. After you troubleshoot all other easy possibilities, try replacing the fuse first.

Can a Bad Battery Cause Lights to Dim?

A dying battery or battery terminals that are loose or corroded can definitely cause the dashboard lights not to work correctly. Usually, they will go very dim while the car is being started. However, a small amount of dimming is normal while the engine is turning over.

Tip: If you need to replace badly corroded or damaged terminals, here are some universal ones found on Amazon.

Usually, if the batter is the issue, other lights besides the dash will also flick or go dim while the car is starting. Your interior lights or headlights will likely go dim or flicker as well.

Check to See if a Battery Replacement Is Due

An alternator will keep your battery charged, but that doesn’t mean it will last forever. A weak or dying battery can cause fluctuations in electricity that, in turn, will dim the lights. The car might continue running smoothly, but the problem is still there.

Most vehicles have a specific light on the instrument panel cluster that will tell you if there is a problem with your battery. If replacing the battery doesn’t fix the issue of dimming while the vehicle is started, it could be an issue is the alternator. If that is the case, it’s time to make an appointment with the mechanic.

However, you may want to read this article that I wrote first: The Cost To Rebuild an Alternator (and Is It Worth It?).

Is It Normal for Headlights to Dim When Using Power Windows?

The headlights shouldn’t dim when you use power windows. It’s a sign that there is an issue with a battery, power connection, or grounding of the battery or window motor. It might be tough to locate the core problem, so it’s best to take your car to a repair shop.

Bottom Line

Your dashboard is designed to give you quick insight into your car’s performance and functionality. The instrument panel notifies a driver about possible dangers, alerts, and other crucial information that allow one to drive safely and comfortably. The brightly colored lights show your engine’s performance, speed, gas level, temperature, and many other aspects. However, what do you do when your dashboard goes dim after turning on your headlights?

If you want to fix your dashboard lights, the first thing you need to do is check your dimmer settings.

To do that, you need to find the dimmer switch or the set of buttons responsible for dashboard lightning. Keep in mind that each vehicle is different. However, often you can find the light switch next to the steering column of the console. Another common location place of the dimmer is as one of the features on the headlight switch. You need to turn the switch or knob to the right to make the dashboard lights brighter.

If that didn’t work, or none of the other potential fixes I mentioned, the entire switch might be faulty. You will need a mechanic to replace the switch. In rare cases, it might also be that your vehicle has a deficient bulb. Or, there might be a loose connection that doesn’t allow the bulb to operate efficiently. Before assuming this is the issue, try replacing the fuse.

I hope you are able to resolve the issue without having to call a mechanic. However, if you do, the problem is often very minor, and the repair cost low. Good luck!

For more, don’t miss How Much Do Rims Cost for a Car? (New and Used).